Content addressable optical data storage system

Abstract

A multidimensional optical storage medium is provided for storing a plurality of holographic images representative of data. An interrogation network generates a search argument including a target data field to be simultaneously searched for over at least a segment of the optical storage medium. The interrogation network couples the search argument into the optical storage medium and extracts a set of address fields at which data fields in the storage medium that match the target data field of the search argument are stored.

Having described the invention, what is claimed as new and secured by Letters patent is: 
     
       1. A content addressable memory system for storage and retrieval of digital data, the system comprising optical storage means including a three or more dimensional holographic storage medium for storing a plurality of holographic images representative of data fields, input means for transmitting information into said holographic storage medium and output means for retrieving information from said holographic storage medium, wherein said holographic storage medium comprises a spectral hole burning material including absorption regions addressed by an interrogating beam of light specifying an address field that includes a wavelength address indicating a wavelength at which a particular data field in said holographic storage medium is stored and a Bragg angle address indicating a Bragg angle at which said particular data field in said holographic storage medium is stored, and   content addressable interrogation means, cooperative with said input means and said output means, operative in at least a first mode, for generating a search argument including a first target data field to be simultaneously searched over at least a segment of said optical storage means containing more than one of said data fields; for presenting said search argument into said holographic storage medium; and for extracting from said output means a set of address fields associated with data fields in said holographic storage medium that match said target data field of said search argument.   
     
     
       2. A system according to claim 1 in which said interrogation means further includes broadband light source means optically coupled to said input means and operative in said first mode for generating a broadband light beam including a plurality of wavelength addresses. 
     
     
       3. A system according to claim 2 in which said interrogation means further includes data specifying means coupled between said broadband light source means and said input means and operative in said first mode for modulating said first target data field onto said broadband light beam at a plurality of Bragg angle addresses. 
     
     
       4. A system according to claim 3 in which said data specifying means includes spatial light modulator means for modulating said first target data field onto said broadband light beam, as an array of essentially bright and essentially dark pixels. 
     
     
       5. A system according to claim 4 in which said spatial light modulator means includes means for encoding said first target data field as an array of ordered pairs of essentially bright and essentially dark pixels, wherein said data specifying means encodes a data bit having a first logical stage as an ordered pair consisting of an essentially dark pixel and an essentially bright pixel and encodes a data bit having a second logical state as an ordered pair consisting of an essentially bright pixel and an essentially dark pixel, and for impressing said array onto said broadband light beam. 
     
     
       6. A system according to claim 5 in which said array includes a plurality of rows and columns and said spatial light modulator means includes means for specifying particular Bragg angle addresses by which of said columns contains said first target data field. 
     
     
       7. A system according to claim 5 in which said spatial light modulator means includes means for specifying an all inclusive condition within said first target data field, said all-inclusive condition being specified as an ordered pair consisting of a first essentially dark pixel and a second essentially dark pixel. 
     
     
       8. A system according to claim 4 in which said spatial light modulator means includes phase encoding means for impressing said first target data field encoded as said array of ordered pairs of essentially bright and essentially dark pixels onto said broadband light beam by selectively rotating the polarity of said broadband light beam. 
     
     
       9. A system according to aim 8 in which said spatial light modulator means includes a two-dimensional array of liquid crystal spatial light modulator elements, wherein each of said modulator elements corresponds to said essentially bright or said essentially dark pixel to be impressed onto said broadband light beam, and each of said modulator elements includes means, responsive to a voltage control signal, for impressing said essentially bright pixel onto said broadband light beam of any of, rotating said broadband light beam by a first polarization and passing said broadband light through said modulator element, and rotating said broadband light beam by a second polarization and passing said broadband light through said modulator element, and each of said modulator elements further includes means, responsive to said voltage control signal, for impressing said essentially dark pixel onto said broadband light beam by blocking said broadband light beam from passing through said modulator element. 
     
     
       10. A system according to claim 9 in which said system includes polarity control means, coupled to said liquid crystal spatial light modulator elements for selecting at each modulator element any of said first polarization and said second polarization to be impressed onto said broadband beam of light. 
     
     
       11. A system according to claim 10 in which said system includes correlation means for correlating data, stored in said holographic medium and having a particular polarization, with test data and for signaling said polarity control means to update said polarization of said data stored in said holographic medium in response to said correlation. 
     
     
       12. A system according to claim 3 in which said interrogation means further includes an output plane means including a light sensitive surface means optically coupled to said output means for producing electrical output signals in response to the location at which one or more light beams are incident upon said light sensitive surface. 
     
     
       13. A system according to claim 12 in which said interrogation means operates to generate and transmit at least one light beam onto said light sensitive surface, the position at which each of said light beams are incident upon said light sensitive surface means being indicative of a Bragg angle address in said holographic storage medium at which said first target data field is stored. 
     
     
       14. A system according to claim 13 in which said output means further includes dispersion means coupled between said beam generation means and said light sensitive surface means for dispersing said light beam, the degree of dispersion being indicative of a wavelength address in said optical storage at which said first target data field is stored. 
     
     
       15. A system according to claim 12 in which said light sensitive surface means includes an array of light sensitive pixels, and means for generating an electrical output signal, wherein said output signal is indicative of a particular combination of said light sensitive pixels being exposed to light. 
     
     
       16. A system according to claim 15 in which said interrogation means includes data reading means for reading from said storage medium said second target data fields previously written to said storage medium, wherein said output means includes means for coupling each of said essentially bright and essentially dark pixels included in said second target data fields to a corresponding light sensitive pixel on said light sensitive surface means. 
     
     
       17. A system according to claim 1 in which said holographic storage medium includes means for storing phase holographic images representative of digital data fields, said phase holographic images being stored in index modulation regions near spectral hole absorption edges. 
     
     
       18. A system according to claim 17 in which said system further includes means for applying an external electric field of specified voltage to said holographic storage medium to induce Stark effect broadening of said spectral hole burning material, so that at a given wavelength of interrogating light, a different holographic image being stored for each of a plurality of voltages. 
     
     
       19. A system according to claim 18 in which said system further includes Stark effect control means for specifying said voltage of the applied electric field. 
     
     
       20. A system according to claim 17 in which said system further includes means for applying a physical stress of specified magnitude to said holographic storage medium to induce broadening of said spectral hole burning material, so that at a given wavelength of interrogating light, a different holographic image can be stored for each of a plurality of stress field magnitudes. 
     
     
       21. A system according to claim 20 in which said system further includes physical stress control means for specifying said magnitude of said physical stress field. 
     
     
       22. A system according to claim 20 in which said means for applying said physical stress further includes at least one piezoelectric element in contact with at least one surface of said holographic storage medium, said piezoelectric element being responsive to an electrical control signal to apply a specified physical stress field to said storage medium. 
     
     
       23. A system according to claim 1 in which said interrogation means further includes neural network means for generating said search argument including said target data field representative of an interconnection encoding between a designated active storage location of a first memory element and a designated active storage location of a second memory element. 
     
     
       24. A system according to claim 1 in which said interrogation means further includes data writing means, operative in a second mode, for writing data fields to said storage medium, and said writing means includes, variable wavelength laser means, operative in said second mode, and coupled to said input means over a first optical path by way of said data specifying means for generating a writing beam of coherent light at a specified wavelength address, and   deflecting means operative in said second mode, and coupled to said variable wavelength laser means for coupling said writing beam of light over a second optical path at a specified Bragg angle address to said storage medium, and   spatial light modulator means includes an array of data bits to be written into said storage medium, and means operative in said second mode for encoding each of said data fields as an array of ordered pairs of essentially bright and essentially dark pixels, wherein said data bits having a first logical state are encoded as an ordered pair consisting of an essentially dark pixel and an essentially bright pixel, and said data bits having a second logical state are encoded as an ordered pair consisting of an essentially bright pixel and an essentially dark pixel, and means or impressing said array of ordered pairs onto said writing beam coupled to said input means over said first optical path.   
     
     
       25. A system according to claim 24 in which said spatial light modulator means includes phase encoding means for impressing said second target data fields encoded as said array of ordered pairs of essentially bright and essentially dark pixels onto said coherent beam of light by selectively rotating the polarity of said writing beam of coherent light. 
     
     
       26. A system according to claim 25 in which said spatial light modulator means includes a two-dimensional array of liquid crystal spatial light modulator elements, wherein each of said modulator elements corresponds to said essentially bright or said essentially dark pixel to be impressed onto said coherent beam of light. 
     
     
       27. A system according to claim 26 in which each of said modulator elements includes polarization means, responsive to a voltage control signal, for impressing said essentially bright and essential dark pixels onto said coherent beam of light by rotating said coherent beam of light. 
     
     
       28. A system according to claim 27 in which said polarization means includes means, responsive to said voltage control signal, for impressing said essentially bright pixel onto said coherent beam of light by rotating said coherent beam of light by a first polarization and passing said coherent beam of light through said modulator element. 
     
     
       29. A system according to claim 28 in which said polarization means includes means, responsive to said voltage control signal, for impressing said essentially bright pixel onto said beam of coherent light by rotating said coherent beam of light by a second polarization and passing said coherent beam of light through said modulator element. 
     
     
       30. A system according to claim 29 in which said polarization means includes means, responsive to said voltage control signal, for impressing said essentially dark pixel onto said coherent beam of light by blocking said coherent beam of light from passing through said modulator element. 
     
     
       31. A system according to claim 26 in which said data writing means includes page address labeling means for writing to said storage medium, with each of said array of data bits, said second target data field having a wavelength address label stored in a specified portion of said array of data bits, and wherein said spatial light modulator means includes means for encoding at least one bit included in said address label as an ordered pair consisting of a first essentially bright pixel having a first specified polarization and a second essentially bright pixel having a second specified polarization. 
     
     
       32. A system according to claim 31 in which said system includes wavelength detection means for determining the wavelength of said coherent beam of light by reading that wavelength address label stored at a wavelength address, in said storage medium, corresponding to the wavelength of said coherent beam of light. 
     
     
       33. A system according to claim 32 in which all of said wavelength address labels are identical and said system includes means for determining the wavelength of said coherent beam of light by applying to said storage means said search argument which matches said address label and by detecting the position of a resulting point image on said output plane. 
     
     
       34. A system according to claim 26 in which said system includes polarity control means, coupled to said liquid crystal spatial light modulator elements for selecting at each modulator element any of a first polarization and a second polarization to be impressed onto said coherent beam of light. 
     
     
       35. A system according to claim 34 in which said system includes correlation means for correlating data, stored in said holographic medium and having a particular polarization, with test data and for signaling said polarity control means to update said polarization of said data stored in said holographic medium in response to said correlation. 
     
     
       36. An optical data storage system for writing and reading data out of and into a storage medium, said system comprising, optical storage means including a multi-dimensional holographic storage medium for storing a plurality of holographic images representative of digital data fields,   variable wavelength laser means coupled to said storage medium for generating a writing beam of coherent at a specified wavelength address, and   deflecting means coupled between said variable wavelength laser means and said storage medium or deflecting said writing beam of light over a first optical path to said storage medium at a specified Bragg angle address, ad   data specifying means coupled between said variable wavelength laser means and said storage medium for modulating a data field, comprising an array of data bits to be written into said storage medium, onto said writing beam, wherein   said data specifying means includes means for encoding said data field as an array of ordered pairs of essentially bright and essentially dark pixels, wherein said data bits having a first logical state are encoded as an ordered pair consisting of an essentially dark pixel and an essentially bright pixel, and said data its having a second logical state are encoded as an ordered pair consisting of an essentially bright pixel and an essentially dark pixel.   
     
     
       37. A system according to claim 36 in which said data specifying means includes means for specifying an all-inclusive condition within said data field, said all-inclusive condition being specified as an ordered pair consisting of a first essentially dark pixel and a second essentially dark pixel. 
     
     
       38. A system according to claim 36 in which said data specifying means further includes phase encoding means or modulating the writing beam by rotating the polarity of said coherent beam of light. 
     
     
       39. A system according to claim 38 in which said data specifying means includes a two-dimensional array of liquid crystal spatial light modulator elements, wherein each of said modulator elements corresponds to said essentially bright or said essentially dark pixel to be impressed onto said coherent beam of light. 
     
     
       40. A system according to claim 39 in which each of said modulator elements includes polarization means, responsive to a voltage control signal, for impressing said essentially bright and essentially dark pixels onto said coherent beam of light by rotating said coherent beam of light. 
     
     
       41. A system according to claim 40 in which said polarization means includes means, responsive to said voltage control signal, for impressing said essentially bright pixel onto said coherent beam of light by rotating said coherent beam of light. 
     
     
       42. A system according to claim 41 in which said polarization means includes means, responsive to said voltage control signal, for impressing said essentially bright pixel onto said coherent beam of light by a first polarization and passing said coherent beam of light through said modulator element, and rotating said coherent beam of light by a second polarization and passing it through said modulator element. 
     
     
       43. A system according to claim 42 in which said polarization means includes means, responsive to said voltage control signal, for impressing said essentially dark pixel onto said coherent beam of light by blocking said coherent beam of light from passing through said modulator element. 
     
     
       44. A system according to claim 39 in which said system includes polarity control means, coupled to said liquid crystal spatial light modulator elements for selecting at each modulator element any of a first polarization and a second polarization to be impressed onto said coherent beam of light. 
     
     
       45. A system according to claim 44 in which said system includes correlation means for correlating data, stored in said holographic medium and having a particular polarization, with test data and for signaling said polarity control means to update said polarization of said data stored in said holographic medium in response to said correlation. 
     
     
       46. A system according o claim 38 in which said data specifying means includes page address labeling means for writing into said storage medium, with each of said array of data bits, said data field having a wavelength address label stored in a specified portion of said array of data bits, and means for encoding at least one bit included in said address label as an ordered pair consisting of a first essentially bright pixel having a first specified polarization and a second essentially bright pixel having a second specified polarization. 
     
     
       47. A system according to claim 46 in which said system includes wavelength detection means for determining the wavelength of said coherent beam of light by reading that wavelength address label stored at a wavelength address, in said storage medium, corresponding to the wavelength of said coherent beam of light. 
     
     
       48. A system according to claim 47 in which all of said wavelength address labels are identical and said system includes means for determining the wavelength of said coherent beam of light by applying to said storage mans said search argument which matches said address label and by detecting the position of a resulting point image on an output plane. 
     
     
       49. An optical interconnection system for storing an interconnection matrix selectably interconnecting an input memory element and an output memory element, each memory element having a set of memory cells arranged in at least two dimensions, the system comprising optical storage means including a multi-dimensional holographic storage medium for storing a plurality of holographic images representative of digital data fields,   variable wavelength writing laser means coupled to said storage medium for generating first and second coherent beams of light at a specified wavelength address,   input connection specifying means coupled between said variable wavelength laser means and said storage medium for modulating a first data field, comprising a first array of data bits indicative of active input memory element locations to be interconnected with active output memory element locations, onto said first coherent light beam, and for coupling said first coherent light beam over a first optical path to said holographic storage medium, and   output connection specifying means coupled between said variable wavelength laser means and said storage medium for modulating a second data field, comprising a second array of data bits indicative of active output memory element locations, onto said second coherent light beam, and for coupling said second coherent light beam over a second optical path to said holographic storage medium, and wherein   said input connection specifying means includes means for encoding said first array of data bits as a first array of ordered pairs of essentially bright and essentially dark pixels, said data bits in said first array which have a first logical state being encoded as an ordered pair consisting of an essentially dark pixel and an essentially bright pixel, and said data bits in said first array which have a second logical state being encoded as an ordered pair consisting of an essentially bright pixel and an essentially dark pixel, and means for modulating said first array of ordered pairs onto said first coherent beam of light, and   said output connection specifying means includes means for encoding said second array of data bits as a second array of ordered pairs of essentially bright and essentially dark pixels, said data bits in said second array which have a first logical state being encoded as an ordered pair consisting of an essentially dark pixel and an essentially bright pixel, and said data bits in said second array which have a second logical state being encoded as an ordered pair consisting of an essentially bright pixel and an essentially dark pixel, and means for modulating said second array of ordered pairs onto said second coherent beam of light.   
     
     
       50. A system according to claim 49 in which at least one of said input connection specifying means and said output connection specifying means includes phase encoding means for encoding phase information by selectively rotating the polarity of at least one of said first coherent beam of light and said second coherent beam of light. 
     
     
       51. A system according to claim 50 in which at least one of said input connection specifying means and said output connection specifying means includes a two-dimensional array of liquid crystal spatial light modulator elements, wherein each of said modulator elements corresponds to said essentially bright or said essentially dark pixel to be impressed onto at least one of said first coherent beam of light and said second coherent beam of light. 
     
     
       52. A system according to claim 51 in which each of said modulator elements includes polarization means, responsive to a voltage control signal for impressing said essentially bright and essentially dark pixels onto the coherent beam of light by rotating that coherent beam of light. 
     
     
       53. A system according to claim 52 in which said polarization means includes means, responsive to said voltage control signal, for impressing said essentially bright pixel onto at least one of said first and second coherent beams of light by rotating that coherent beam of light by a first polarization and passing that coherent beam of light through said modulator element. 
     
     
       54. A system according to claim 53 in which said polarization means includes means, responsive to said voltage control signal, for impressing said essentially bright pixel onto at least one of said first and second coherent beams of light by rotating that coherent beam of light by a second polarization and passing that coherent beam of light through said modulator element. 
     
     
       55. A system according to claim 54 in which said polarization means includes means, responsive to said voltage control signal, for impressing said essentially dark pixel onto a coherent beam of light by blocking said coherent beam of light from passing through said modulator element. 
     
     
       56. A system according to claim 51 in which at least one of aid input connection specifying means and said output connection specifying means includes page address labeling means for writing into said storage medium, with each of said array of data bits, said data field having a wavelength address label stored in a specified portion of said array of data bits, and means for encoding at least one bit included in said address label as an ordered pair consisting of a first essentially bright pixel having a first specified polarization and a second essentially bright pixel having a second specified polarization. 
     
     
       57. A system according to claim 56 in which said system includes wavelength detection means for determining the wavelength of said coherent beam of light by reading that wavelength address label stored at a wavelength address, in said storage medium, corresponding to the wavelength of said coherent beam of light. 
     
     
       58. A system according to claim 57 in which all of said wavelength address labels are identical and said system includes means for determining the wavelength of said coherent beam of light by applying to said storage means a search argument which matches said address label and by detecting the position of a resulting point image on an output plane. 
     
     
       59. A system according to claim 51 in which said system includes polarity control means, coupled to said liquid crystal spatial light modulator elements for selecting at each modulator element any of a first polarization and a second polarization to be impressed onto said coherent beam of light. 
     
     
       60. A system according to claim 59 in which said system includes correlation means for correlating data stored in said holographic medium and having a particular polarization with test data, and for signaling said polarity control means to update said polarization of said data stored in said holographic medium in response to said correlation. 
     
     
       61. A system according to claim 50 in which at least one or said input connection specifying means and said output connection specifying means includes means or specifying an all-inclusive condition within said data field, said all-inclusive condition being specified as an ordered pair consisting of a first essentially dark pixel and a second essentially dark pixel.